In previous GSM data connections, in particular for digitized voice data between mobile stations over a communication network such as the public telephone. network (PSTN--Public Switched Telephone Network), the GSM data in GSM format are converted into the frame format of the communication network--64 kbit/s PCM for PSTN--using a transcoder. For DMCS 900 mobile radio systems, such transcoding is performed at the base stations, or the A interface with the PSTN communication network. Pursuant to GSM recommendation 0860/0861, digital voice transmission takes place in "TRAU (Transcode and Rate Adaptor Unit) frames," i.e., in 16 kbit/s format transmission frames at FR (Full Rate) transmission and 8 kbit/s or 16 kbit/s at HR (Half Rate) transmission.